Pendulum type sensors of the general type disclosed herein are shown in U.S. Pat. Nos. Porter et al 3,717,731 issued Feb. 20, 1973; Porter 3,717,732 issued Feb. 20, 1973; Brooks et al 3,678,763 issued July 23, 1972; Orlando 3,710,051 issued Jan. 9, 1973; and U.S. patent application Ser. No. 002,946 filed Jan. 12, 1979. Generally such sensors include an acceleration responsive mass which is suspended by a deflectable wire with a sector shaped recess. Either a magnet or the deflection of the wire or both provides a preload bias on the mass normally locating the mass in unactuated position in engagement with the walls of the recess adjacent the proximal end thereof. Electrical contacts located adjacent the distal end of the recess are engaged by the mass to close an electrical circuit when the mass is subjected to a pulse of predetermined amplitude and time sufficient to overcome the preload bias and move the mass through the recess and into engagement with the contacts.